Many heat exchangers today, as, for example, vehicular radiators, employ so called flattened tubes extending between opposed headers. Serpentine fins are disposed between and bonded to the flattened tubes on the flat side walls thereof.
In operation, the fluid within the heat exchanger, typically an engine coolant, receives heat rejected from the heat source such as an internal combustion engine and as a consequence, has its temperature elevated. This, in turn, means that the internal pressure within the heat exchanger is likewise elevated. Because the tubes are flattened, internal pressures will be acting against a flat inner surface of the flat side walls of the tubes and as is well known, this pressure will tend to make the tubes "go round".
In plate fin heat exchangers, the plate fins provide necessary pressure restraint by positively confining the tube side walls. Serpentine fins, however, may have insufficient strength to confine the tubes to prevent the tube minor dimensions from expanding in response to pressure. As a consequence, upon pressurization, a heat exchanger may tend to "grow" in the direction transverse to the direction of the elongation of the tubes.
To avoid this problem, heat exchangers are conventionally provided with side pieces which sandwich the tubes and the serpentine fins. The side pieces typically extend between the headers as do the tubes, and are frequently formed of channels for enhanced rigidity. Thus, expanding forces transverse to the direction of elongation of the tubes may be transmitted to the side pieces of the resulting heat exchanger core to be resisted by the strength provided by the side pieces, as well as the headers themselves which may serve to anchor opposite ends of the side pieces in many heat exchanger constructions.
While this type of constraint works well in a number of instances, generally, its success is limited to relatively small heat exchangers having relatively short tubes and side pieces. In larger heat exchangers having relatively long tubes and side pieces, it is generally been necessary to increase the rigidity of the side pieces to resist the deformation due to internal pressure within the heat exchanger. This in turn has increased the cost of heat exchangers as a result of the additional material required. It has also increased the weight of heat exchangers for the same reason.
The present invention is directed to overcoming one or more of the above problems.